Many aircraft include an external door for accessing an aircraft cargo area. Cargo areas typically utilize upward-opening, canopy-style doors, as opposed to the side-opening, plug-style doors used for passenger ingress and egress. Many forms of doors exist for cargo loading and unloading; however, these designs suffer from a number of weaknesses, including susceptibility to malfunction caused by icing of door components, leading to the possibility that an aircraft may take off with a door improperly secured. Previous designs have used cable-actuated monitoring systems to indicate successful door closure; however, these designs are subject to malfunction due to icing. The difficulty in creating a hermetic seal between the actuating cable and the cable housing leads to formation of ice inside the cable housing, rendering the cable inoperative. Additionally, prior designs have utilized latching systems that require a dwell in the latching actuation. This introduces additional cost and complexity into the design. Because these latching systems are independent of the locking systems, additional parts and interface requirements are needed. Furthermore, existing designs do not provide an independent lock for the latch system, leading to the possibility that ground loads or in-flight forces could create a torque on the system and possibly unlatch the door in the event of a failure in the lock system.
A need, therefore, exists for an integrated latching/locking system that minimizes parts count and complexity, while eliminating the reliability issues caused by icing or other adverse conditions.